Downgraded to Windows 8.1 from Windows 10 but Windows update keeps wanting to reinstall Windows 10, how can I stop this message?

when windows rebooted after the downgrade it immediately went into Windows update and began downloading windows 10 then said ready to install windows 10 with a get satrted option available. I have not been able to change this and get any windows 8.1 updates. I want to be able to remove any requests to downlaod and install windows 10. Have already had one session with tech support from Microsoft and they were unable to fix the problem so far.